Microelectronic devices are generally complex, delicate components used in larger products. A typical microelectronic device includes a microelectronic die, a support structure attached to the die, and a protective casing encapsulating the die. The microelectronic die can be a semiconductor device (e.g., a microprocessor or a memory device), a field emission display, or another type of device. The support structure is generally a lead frame having a plurality of leads or an interposing substrate having electrically conductive traces and solder ball pads. The protective casing is generally a hard plastic, such as a thermosetting material, that is molded around the die. The protective casing encapsulates the die and a portion of the support structure to protect the die from environmental hazards and physical shocks.
The microelectronic dies include integrated circuitry and a plurality of bond-pads that are coupled to the integrated circuitry. In a typical application for a DRAM memory device, a die will have a reference voltage (Vref) bond-pad, a plurality of supply voltage (Vdd) and ground voltage (Vss) bond-pads, a plurality of signal bond-pads (e.g., clock lines, address lines, and data lines), a column address strobe (CAS) bond-pad, and a row address strobe (RAS) pad. The bond-pads are often arranged in a fine pitch array on one side of the die, and each bond-pad is coupled to the appropriate voltage source or signal source. For example, the Vref bond-pad is coupled to a reference voltage source, the Vss and Vdd bond-pads are coupled to appropriate electrical potentials, and the signal bond-pads are coupled to the correct signal sources. The support structures are accordingly configured so that the leads or traces couple the bond-pads on the die to the corresponding voltage and signal sources.
The trend in microchip fabrication is to manufacture smaller and faster microelectronic dies for computers, cell phones, PDAs, and many other products. As the dies become faster and have larger capacities, the components of the integrated circuitry are much smaller and spaced closer together so that more components can be fabricated in the dies. The high densities of components and fast operating speeds increase the amount of heat produced by the dies. High performance microelectronic devices accordingly generate a significant amount of heat during operation.
A significant limiting factor for operating packaged microelectronic devices is dissipating the heat generated by high performance dies. The dies are sensitive components that are typically protected from physical contact and environmental conditions to avoid damaging the die. In many applications, the protective casings seal the die from environmental factors (e.g., moisture) and shield the die from electrical and mechanical shocks. The protective casings, however, also retain the heat generated by the dies. This may cause high performance dies to overheat to the extent that the dies malfunction or are damaged.
One conventional technique to dissipate the heat from packaged devices is to bond a heat sink to an external surface of the casing encapsulating a die. The heat sink is typically attached to the casing using an epoxy or other adhesive. One drawback of this is that the heat generated by high performance dies may raise the temperature of the epoxy to a level at which it fails. Therefore, existing packaged microelectronic devices with heat sinks do not provide adequate solutions for operating high performance dies.